[time-nuts] WWVB PM Time Questions

[rodger_adams at yahoo.com]

Hey Ray, 

Paul and I have a nice piece of code that generates the WWVB BPSK bit stream
using an Arduino and a ublox GPS module. (total cost under $30)  You could
use this as a WWVB emulator while you're working on your code.  Sorry, I
can't really help with your question about demodulating the WWVB BPSK but
the Costas loop sounds like the way to go.  It has also been suggested that
a WWVB SDR wouldn't be too difficult to build and would open up lots of
possibilities.  Unfortunately, I don't have a clue where to begin with that.
Maybe somebody with some SDR experience can chime in.

Re your comment about $30 BPSK clocks.  The only clock I'm aware of that
uses the BPSK is the Lacrosse Ultratomic.  Are you aware of any others?

Thanks,

Rodger

-----Original Message-----
From: time-nuts <time-nuts-bounces at lists.febo.com> On Behalf Of
rcbuck at atcelectronics.com
Sent: Tuesday, July 21, 2020 11:52 PM
To: Discussion of precise time and frequency measurement
<time-nuts at lists.febo.com>
Subject: Re: [time-nuts] WWVB PM Time Questions

Paul, thanks for the suggestions. The top of the minute is a good idea.
Since the first second is part of the sync pattern it will always be 0 and
the phase would be 0. A differential opamp with one input from WWVB and the
other from the local source fed to the STM32 would tell if the signals were
in phase. A single gate inverter controlled by the STM32 could be used to
invert the local source if necessary.

I have worked with the Bluepill for the last year on a few small projects.
The most complex one (which isn't really complex) was to control two stepper
motors. I really like the boards and you can't beat the prices. I don't use
the bootloader so I have no experience with it.

Dana, I looked at the Costas loop and had sort of ruled it out. I may take
another look at it as I get further into the project. I will probably use a
15.360 MHz oscillator and divide by 256 to get the 60 kHz local source. Once
I get the front end working I will be able to start some "real" testing.

Suggestions from others are welcome.

Ray,
AB7HE



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